Radio communication system, radio terminals, radio base stations, radio communication method and program

ABSTRACT

Disclosed is a radio communication system wherein radio terminals can communicate using a plurality of component carriers having different frequencies. The communication system has a reception start timing control means for commonly controlling the cycle of reception start timing for predetermined channels in at least some of the component carriers assigned to the radio terminals; and a reception control means for controlling the reception interval of said predetermined channels, said reception intervals being started at the reception start times in at least some of the component carriers assigned to the radio terminals.

This is a divisional application based upon U.S. patent application Ser.No. 13/499,526 filed Mar. 30, 2012, which is a National Stage ofInternational Application No. PCT/JP2010/067062 filed Sep. 30, 2010,claiming priority based on Japanese Patent Application No. 2009-230114filed Oct. 2, 2009, the contents of all of which are incorporated hereinby reference in their entirety.

TECHNICAL FIELD

The present invention relates to a radio communication system, a radioterminal, a radio base station, a radio communication method, and aprogram therefor.

BACKGROUND ART

The radio terminal is supported with a DRX functionality (DRX:Discontinuous Reception) in 3 GPP LTE (Long Term Evolution), being oneof next-generation cellar systems, so as to reduce power consumption ofthe radio terminal (Non-patent literatures 1 and 2). In the LTE, aperiod called a DRX cycle that consists of a reception period(On-Duration) and a non-reception period subsequent hereto (Opportunityfor DRX) is defined, and repeating these periods allows the DRX to berealized.

The radio terminal shall receive a downlink control channel (PDCCH:Physical Downlink Control Channel) at any time in the On-Duration, anddoes not need to receive it in the Opportunity for DRX. Additionally,when the radio terminal fails in receiving data during the On-Durationand yet the above data is retransmitted after the On-Duration period, itextends the period in which the PDCCH is received.

Herein, the period in which the radio terminal under DRX operationreceives the PDCCH is called Active Time, and the On-Duration is aminimum value of the Active Time. In addition, two DRX states (levels),i.e. “ShortDRX” and “LongDRX” each having a different length of theOpportunity for DRX can be set for each radio terminal. When the radioterminal in a ShortDRX state does not receive the data for a constantperiod, the LTE takes a DRX state control for transiting to a LongDRXstate. Further, a timer (drxShortCycleTimer) is used for determining astate transition from the ShortDRX to the LongDRX. This makes itpossible to set the DRX state (level) suitable for a data receptionfrequency of the radio terminal, and to realize a reduction of powerconsumption of the radio terminal.

In addition, as the cellar system having the LTE sophisticated therein,LTE-Advanced is standardized. As one of the LTE-AdvancedFunctionalities, there exists carrier aggregation (Carrier Aggregation:CA) for performing data transmission/reception by simultaneously using aplurality of the component carriers (Component Carrier: CC) for oneradio terminal, which serves as a functionality of enhancing a peak daterate for each radio terminal (Non-patent literature 3). Herein theso-called CC is a basic frequency block necessary for realizing thecommunication between the radio base station and the radio terminal inthe LTE. When the CA is carried out, one transport block (a unit fortransferring data from an MAC layer to a PHY layer) istransmitted/received on one CC, and a signal process is independentlyperformed for each CC. Additionally, when HARQ is carried out becauseretransmission of the data is required, the CC used for the firsttransmission is identical to the CC used for the retransmission.

At present, in 3GPP Standardization, a discussion about the DRX of theradio terminal at the time of the CA is underway, and a method ofcarrying out identical DRX configuration (setting of a DRX parameter) toall the CCs for performing the Carrier Aggregation (CA) is beinginvestigated. As an actual method of the DRX control (an Active Timecontrol and a DRX state control), a method (A) of cooperatively taking acontrol among the CCs for performing the CA (Non-patent literature 5)and a method (B) of independently taking a control on each CC(Non-patent literature 6) are proposed. In the method (A) ofcooperatively taking a control among the CCs, the DRX state control iscommonly taken among the CCs by aligning the Active Time on all the CCsto that of the CC on which the data has been received to the end. On theother hand, in the method (B) of independently taking a control on eachCC, the Active Time of each CC is decided based on a data receptionsituation on each CC, and the DRX state control is also takenindependently on each CC.

An example of the method (A) of cooperatively taking a control among theCCs for performing the CA will be explained by employing FIG. 24.

This figure shows a situation in which a certain radio terminal isassigned CC1 to CC3 as the CC for performing the CA and the radioterminal is ready for reception of DL data on all these CCs. Further, aDRX parameter on each CC is identical, and starts of respective DRXcycles are synchronized with each other among the CCs. Upon payingattention to a first-place DRX cycle of the CC1, the Active Time isextended so that the retransmission data can be received because the DLdata was not able to be successfully decoded notwithstanding thereception of the DL data in the On-Duration. And, the CC1 transits tothe non-reception period (Opportunity for DRX) in which the PDCCH doesnot need to be received when the retransmission data can be successfullydecoded.

Next, upon paying attention to the operations on the CC2 and the CC3 atthe DRX cycle having the identical timing, no data is received on theCC2, and the data is received on the CC3 similarly to the CC1. At thistime, upon viewing the CC2 and the CC3 separately, there is no necessityfor extending the Active Time beyond the On-Duration on the CC2, and theActive Time is extended on the CC3; however the Active Time of the CC3may be shorter than that of the CC1.

However, in the method (A), all the Active Times of the CC1 to CC3 areones depicted by dotted lines in the figure because the Active Times ofthe CC2 and the CC3 are decided so as to match with that of the CC1requiring the longest Active Time. Herein, the hatching portion in thefigure is the Active Time that has been originally unnecessarilyextended for the above CC. The situation is similar with thesecond-place DRX cycle and the third-place DRX cycle as well, the ActiveTime is controlled so as to match with that of the CC3 at thesecond-place DRX cycle and with the CC2 at third-place DRX cycle,respectively.

Next, an example of the method (B) of independently taking a control oneach CC will be explained by employing FIG. 25.

Similarly to FIG. 24, the radio terminal is ready for reception of theDL data on the CC1 to CC3, the DRX parameter is identical on each CC,and the starts of respective DRX cycles are synchronized with each otheramong the CCs. In addition, it is assumed that the radio terminal isfirstly in a state of the ShortDRX, and transits to the LongDRX when thedata is not received over three-time ShortDRXs (the length ofdrxShortCycleTimer is equivalent to three times that of the ShortDRXcycle).

Upon paying attention to the first-place DRX cycle, thedrxShortCycleTimers are independently started on all the CCs. The datais received on the CC1 and the CC3, and the drxShortCycleTimer isrestarted after the data reception is completed (it is again startedfrom the initial value). The data is not received on the CC2, wherebythe timer is successively running as is. In such a manner, thedrxShortCycleTimer is activated on each CC. The CC3, on which thedrxShortCycleTimer expires at the fifth-place DRX cycle earliest,transits to the LongDRX, and the CC1 transits to the LongDRX at thesixth-place DRX cycle. On the other hand, the CC2 receives the data alsoat the sixth-place DRX cycle with still the state of the ShortDRX.

As a result, only the CC2 can be used at the seventh-place DRX cycle andthe eighth-place DRX cycle, and the CC1 and the CC3 cannot be usedbecause they are in the non-reception period of the LongDRX.Additionally, it is at a timing of the On-Duration next to the LongDRXcycle that the CC1 and the CC3 can be used again.

CITATION LIST Non-Patent Literature

-   NON-PTL 1: 3GPP TS36.300v900 (internet<URL>    http:www.3gpp.org/ftp/Specs/html-info/36300.htm)-   NON-PTL 2: 3GPP TS36.321v860 (internet<URL>    http:www.3gpp.org/ftp/Specs/html-info/36321.htm)-   NON-PTL 3: 3GPP TR36.814v100 (internet<URL>    http:www.3gpp.org/ftp/Specs/html-info/36814.htm)-   NON-PTL 4: 3GPP TR36.331v860 (internet<URL>    http:www.3gpp.org/ftp/Specs/html-info/36331.htm)-   NON-PTL 5: 3GPP RAN2#67 Shenzhen China, “DRX in LTE-A”, Motorola    (internet<URL>    http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_67/Docs/R2-094736.zip)-   NON-PTL 6: 3GPP RAN2#67 Shenzhen China, “Consideration on DRX”, CATT    (internet<URL>    http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_67/Docs/R2-094327.zip)

SUMMARY OF INVENTION Technical Problem

Hereinafter, the related technologies in accordance with the presentinvention are analyzed.

At first, there exist two points that are important in investigating theDRX control with the use of the Carrier Aggregation (CA). The firstpoint is that the DRX state (an index indicative of the ShortDRX or theLongDRX. It is also called a DRX level) of the radio terminal should besame among the Component Carriers (CCs). The reason is that the data isnot received at any time on all the CCs at the time of the CA, and theDRX state should be decided based on not a data reception frequency oneach CC but a total data reception frequency of the radio terminalnotwithstanding a possibility that a data reception frequency on each CCmight differ due to a difference of the communication channel qualityamong the CCs and a load distribution.

And, the second point is that the Active Time should be decided for eachCC at each DRX cycle. The reason is to avoid extending the Active Timebeyond the On-Duration so as to match with the other CCs notwithstandingno possibility of the data reception, and to enable the radio terminalto realizes a reduction of power consumption as much as possible.

Out of the above-described DRX control methods, while the method (A) ofcooperatively taking a control among the CCs used for performing the CAhas an advantage that the DRX state is identical among the CCs, it hasan a disadvantage that the radio terminal excessively consumes the poweron the CC in which the data is not received because the Active Time ateach DRX cycle is also identical among the CCs.

On the other hand, while the method (B) of independently taking acontrol on each CC has an advantage that an effect of a reduction of thepower consumption of the radio terminal is achieved at each DRX cyclebecause the Active time is independent for each CC, it has adisadvantage that the DRX state might differ among the CCs.

In such a manner, the above-described DRX control methods (A) and (B)when the CA is performed have the advantage/disadvantage, respectively,the method (A) of cooperatively taking a control among the CCs forperforming the CA is preferred from a viewpoint of the DRX statecontrol, being the first point, and the method (B) of independentlytaking a control on each CC is preferred from a viewpoint of a reductionof power consumption of the radio terminal, being the second point.

Judging from the analysis mentioned above, it cannot be safely said thateach of the above-described DRX control methods, which is capable ofaccomplishing only one of the two important points, is an optimum DRXcontrol method at the time of the CA.

Thereupon, the present invention has been accomplished in considerationof the above-mentioned problems, and an object thereof is to provide aradio communication system, a radio terminal, a radio base station, aradio communication method, and a program therefor that reduce the powerconsumption of the radio terminal while coping with the communicationover a plurality of the component carriers.

Solution to Problem

The present invention is radio communication system in which a radioterminal is configured to communicate using a plurality of carriercomponents each having a different frequency, comprising: a receptionstart timing control means that commonly controls a cycle of a receptionstart timing for a predetermined channel among at least one part of thecomponent carriers assigned to the radio terminal: and a receptioncontrol means that controls a reception period for said predeterminedchannel on at least one part of the component carriers assigned to saidradio terminal, said reception period being started from said receptionstart timing.

The present invention is a radio terminal capable of communicating usinga plurality of carrier components each having a different frequency,comprising: a reception start timing control means that commonlycontrols a cycle of a reception start timing for a predetermined channelamong at least one part of the component carriers assigned to the radioterminal; and a reception control means that controls a reception periodfor said predetermined channel on at least one part of the componentcarriers assigned to said radio terminal, said reception period beingstarted from said reception start timing.

The present invention is a radio base station for transmitting/receivingdata to/from a radio terminal capable of communicating using a pluralityof component carriers each having a different frequency that comprises areception start timing control means for commonly controlling a cycle ofa reception start timing for a predetermined channel among at least onepart of the component carriers assigned to said radio terminal, and areception control means for controlling a reception period for saidpredetermined channel to be started from said reception start timing onat least one part of the component carriers assigned to said radioterminal, said radio base station comprising a means that takessynchronization with the cycle of the reception start timing for thepredetermined channel to be controlled by said radio terminal.

The present invention is a radio communication method in which a radioterminal is configured to communicate using a plurality of componentcarriers each having a different frequency, comprising: commonlycontrolling a cycle of a reception start timing for a predeterminedchannel among at least one part of the component carriers assigned tothe radio terminal; and controlling a reception period for saidpredetermined channel on at least one part of the component carriersassigned to said radio terminal, said reception period being startedfrom said reception start timing.

The present invention is a program of a radio terminal capable ofcommunicating using a plurality of component carriers each having adifferent frequency, said program causing the radio terminal to execute:a reception start timing control process of commonly controlling a cycleof a reception start timing for a predetermined channel among at leastone part of the component carriers assigned to the radio terminal; and areception control process of controlling a reception period for saidpredetermined channel on at least one part of the component carriersassigned to said radio terminal, said reception period being startedfrom said reception start timing.

Advantageous Effect of Invention

The present invention makes it possible to reduce the consumption powerof the radio terminal while coping with the communication over theplural component carriers.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a configuration of a first radiocommunication system of a first exemplary embodiment of the presentinvention.

FIG. 2 is a block diagram of the radio terminal (UE) in the firstexample in accordance with the present invention.

FIG. 3 is a block diagram of the radio base station (eNB) in the firstexample in accordance with the present invention.

FIG. 4 is a view for explaining an operation of the discontinuousreception (DRX) of the radio terminal in the LTE.

FIG. 5 is a view for explaining the Active Time in the DRX of the radioterminal in the LTE.

FIG. 6 is a view for explaining a DRX state transition of the radioterminal in the LTE.

FIG. 7 is a view for explaining a DRX operation of the radio terminal inthe first example in accordance with the present invention.

FIG. 8 is a flowchart of the radio terminal in the first example inaccordance with the present invention.

FIG. 9 is a flowchart of the radio base station in the first example inaccordance with the present invention.

FIG. 10 is a view for explaining the DRX operation of the radio terminalin a modified example of the first example in accordance with thepresent invention.

FIG. 11 is a view for explaining the DRX operation of the radio terminalin a second example in accordance with the present invention.

FIG. 12 is a flowchart of the radio terminal in the second example inaccordance with the present invention.

FIG. 13 is a flowchart of the radio base station in the second examplein accordance with the present invention.

FIG. 14 is a view for explaining the DRX operation of the radio terminalin a third example in accordance with the present invention.

FIG. 15 is a flowchart of the radio terminal in the third example inaccordance with the present invention.

FIG. 16 is a flowchart of the radio base station in the third example inaccordance with the present invention.

FIG. 17 is a view for explaining the DRX operation of the radio terminalin a modified example of the third example in accordance with thepresent invention.

FIG. 18 is a view illustrating a configuration of a second radiocommunication system of another exemplary embodiment of the presentinvention.

FIG. 19 is a view for explaining the DRX operation of the radio terminalin a fourth example in accordance with the present invention.

FIG. 20 is a view illustrating a configuration of a third radiocommunication system of another exemplary embodiment of the presentinvention.

FIG. 21 is a view for explaining the DRX operation of the radio terminalin a fifth example in accordance with the present invention.

FIG. 22 is a flowchart of the radio terminal in the fifth example inaccordance with the present invention.

FIG. 23 is a flowchart of the radio base station in the fifth example inaccordance with the present invention.

FIG. 24 is a view for explaining the DRX operation of the radio terminalin a conventional example.

FIG. 25 is view for explaining the DRX operation of the radio terminalin another conventional example.

FIG. 26 is a view for explaining an outline of the present invention.

FIG. 27 is a view for explaining an outline of the present invention.

DESCRIPTION OF EMBODIMENTS

An outline of the present invention will be explained.

As shown in FIG. 26, the present invention is a radio communicationsystem in which the radio terminal can communicate using a plurality ofthe component carriers each having a different frequency, and the aboveradio communication system includes a reception start timing controllerA that commonly controls a cycle of a reception start timing for apredetermined channel among at least one (a) part of the componentcarriers assigned to the radio terminal, and a reception controller Bthat controls a reception period for the predetermined channel to bestarted from the reception start timing on at least one (a) part of thecomponent carriers assigned to the radio terminal.

Herein, with regard to the component carrier, being a target of thecontrol by the present invention, all component carriers assigned to theradio terminal may be controlled as a target of control, and apredetermined specific carrier may be controlled as a target of control.In addition, the component carriers assigned to the radio terminal maybe divided into several sets to take a control for each set.

Additionally, the so-called component carrier assigned to the radioterminal is a component carrier having a possibility that the data forthe above radio terminal is transmitted, which has been indicated(Configured or Activated) by the radio base station, and/or a componentcarrier on which the above radio terminal receives (or shall receive) apredetermined channel in order to receive the data. Further, it is alsopossible to call a plurality of the component carriers each having adifferent frequency a carrier set. In addition, it is also possible tothink that the so-called communication is data transmission and/or datareception.

With regard to the cycle of the reception start timing, at least twocycles or more of the reception start timing each having a differentcycle length are used, and one cycle of the reception start timing isused among the component carriers each of which is a control target.

Further, with regard to the selection of the cycle of the receptionstart timing, the cycle is desirably decided based on the total datareception frequency of the component carriers each of which is thecontrol target.

Upon explaining one example, when the new data is not received for apredetermined period on at least one part of the component carriersassigned to the radio terminal, the reception start timing controller Atransits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing. This example will beexplained by employing FIG. 27.

FIG. 27 illustrates that the control-target component carriers, out ofthe component carriers assigned to the radio terminal, are a componentcarrier 1, a component carrier 2, and a component carrier 3. And, eachof the component carriers 1, 2, and 3 receives the signals to betransmitted in a predetermined channel either at the cycle of the firstreception start timing or at the cycle of the second reception starttiming which is longer than the cycle of this first reception starttiming; however it is assumed that each of the component carrier 1, 2,and 3 firstly receives the signals to be transmitted in a predeterminedchannel at the cycle of the first reception start timing.

Further, with regard to each of the component carriers 1, 2, and 3,after receiving the data that is transmitted in a predetermined channelor the data that is transmitted correspondingly to the signalstransmitted in a predetermined channel, for example, after the abovedata is successfully decoded, the measurement of a predetermined periodis started. While this measurement is normally made with the timer etc.,any kind timer, for example, a count-up timer and a count-down timer maybe used so long as the predetermined expiry of the period can begrasped. In addition, the measurement may be started not after the datais successfully decoded, but after the retransmission control of thedata (the reception processing in this case) is completed.

On the component carrier 1, the data is received at the first-place, thesecond-place, and the third-place cycles of the first reception starttiming, and is not received for a predetermined period after the datareceived at the third-place cycle of the first reception start timing issuccessfully decoded. Likewise, on the component carrier 3, the data isreceived at the first-place and the second-place cycles of the firstreception start timing, and is not received for a predetermined periodafter the data received at the second-place cycle of the first receptionstart timing is successfully decoded.

On the other hand, on the component carrier 2, the data is received atthe second-place, the third-place, and the fourth-place cycles of thefirst reception start timing, and is received prior to expiry of apredetermined period after the data received at the fourth-place cycleof the first reception start timing is successfully decoded.

Thus, while the new data is not received for a predetermined period onthe component carriers 1 and 3, the data is received prior to expiry ofa predetermined period on the component carrier 2, whereby a transitionto the cycle of the second reception start timings from the cycle of thefirst reception start timings is not carried out.

Continuously, on the component carrier 2, the data is received at theseventh-place cycle of the first reception start timing, and is notreceived for a predetermined period after the data received at theseventh-place cycle of the first reception start timing is successfullydecoded. Likewise, on the component carrier 1, the data is received atthe eighth-place cycle of the first reception start timing, and is notreceived for a predetermined period after the data received at theeighth-place cycle of the first reception start timing is successfullydecoded. Likewise, on the component carrier 3, the data is received atthe eighth-place cycle of the first reception start timing, and is notreceived for a predetermined period after the data received at theeighth-place cycle of the first reception start timing is successfullydecoded.

Thus, the new data is not received for a predetermined period on all thecomponent carriers 1, 2, and 3, whereby a transition to the cycle of thesecond reception start timing from the cycle of the first receptionstart timing is carried out.

In such a manner, the cycle of the reception start timing of apredetermined channel can be shared among the component carriers, andyet the power consumption of the radio terminal can be reduced.

Hereinafter, the exemplary embodiments of the present invention will beexplained with a reference to the accompanied drawings. Additionally, inthe following exemplary embodiments, “3GPP LTE (Long Term Evolution)” isexpected as the radio communication system (cellular system).

The Radio Communication System of the First Embodiment

FIG. 1 is a view illustrating an example of a schematic configuration ofthe radio communication system of the first exemplary embodiment.

This radio communication system of the first exemplary embodimentincludes a radio base station eNB1 (eNB: evolved NodeB) and a radioterminal UE1 (UE: User Equipment). Herein, the UE1 has completed aconnection establishment (RRC Connection) for communicating with theeNB1. Further, the UE1 is assigned CC1 to CC3 as the component carriercapable of carrying out the carrier aggregation (CA: CarrierAggregation), and is already in a state of being able to simultaneouslyreceiving the data on the CC1 to the CC3. Additionally, each frequencyof CC1 to CC3 may be continuous or discontinuous, and in addition, eachfrequency band may be identical or different. In addition, the eNB1notifies a parameter of the discontinuous reception (DRX: DiscontinuousReception) to the UE1, and the UE1 carries out the necessaryconfiguration (for example, setting of expiry values of the DRX-relatedtimers, and the like) according to the above parameter. At this time,the parameter of the DRX is common to the CC1 to the CC3.

FIG. 2 is a block diagram of the radio terminal (UE) in the radiocommunication system of the first exemplary embodiment, and FIG. 3 is ablock diagram of the radio base station (eNB) of the first exemplaryembodiment.

In FIG. 2, the UE1 is configured of a receiver 11, a transmitter 12, asignal processor 13, and a communication controller 14.

The receiver 11 and the transmitter 12 are a portion thatreceives/transmits radio signals from/to the eNB1, respectively. Thesignal processor 13 is a portion that generates the radio signals fortransmitting certain information to the eNB, and recovers originalinformation from the received radio signals. The communicationcontroller 14 is a portion that gives an instruction for generation oftransmission signals, recovery of information, and the like to thesignal processor 13, and the DRX control of the UE is also managed bythis communication controller 14.

In FIG. 3, the eNB1 is configured of a receiver 21, a transmitter 22, asignal processor 23, a communication controller 24, and a terminalmanager 25. Basically, the receiver 21, the transmitter 22, the signalprocessor 23, and the communication controller 24 have a functionalitysimilar to that of the UE1, respectively. Further, the terminal manager25 manages each of a plurality of the UEs separately.

Each of FIG. 4 to FIG. 6 is a view illustrating an operation of thediscontinuous reception (DRX: Discontinuous Reception) of the radioterminal in the radio communication system of the first exemplaryembodiment.

At first, as shown in FIG. 4, the DRX cycle, being a cycle of thediscontinuous reception, is configured of the period (On-Duration) inwhich a downlink control channel PDCCH (Physical Downlink ControlChannel) needs to be received continuously, and the period (Opportunityfor DRX) in which the PDCCH does not need to be received. Additionally,the former is also called a Wake up period, and the latter is alsocalled a Sleep period. Further, the latter could be a period in whichthe PDCCH is not received, or a period in which the reception of thePDCCH is prohibited.

Additionally, the data is transmitted in PDSCH (Physical Downlink SharedChanel), and scheduling information of the PDSCH is contained in thePDCCH. Thus, after the PDCCH is received and the scheduling informationis detected, the data indicated by it can be received.

Herein, the reception start timing of a predetermined channel isequivalent to the start timing of the On-Duration, and the cycle of thereception start timing of a predetermined channel is equivalent to thecycle of the start timing of the On-Duration. Further, the minimum valueof the reception period of a predetermined channel is equivalent to theOn-Duration.

In addition, the so-called reception of a predetermined channel may bementioned in another word, namely, monitoring of the signals to betransmitted in a predetermined channel.

Further, there are two kinds for the DRX cycle, namely, ShortDRX andLongDRX. The ShortDRX and the LongDRX are identical to each other in thelength of the On-Duration, and differ from each other in the length ofthe duration other than the On-Duration in which the PDCCH does not needto be received, and an interval of the On-Duration of the ShortDRX isset so that is becomes shorter than that of the LongDRX. Additionally,in the LTE, there is a constraint that the length of the LongDRX is anintegral multiple of that of the ShortDRX. The length of the On-Durationand the length of the DRX cycle are specified in the Non-patentliterature 4. For example, ten and several types of the lengths of theOn-Duration can be set in a range from 1 ms to 200 ms, and ten andseveral types of the lengths of the DRX cycle can be set in a range from2 ms (the ShortDRX is minimized) to 2560 ms (the LongDRX is maximized)with regard to the ShortDRX and the LongDRX, respectively.

Herein, in addition to the above-described examples, similarly to theOn-Duration, the case of receiving not the downlink control channel suchas the PDCCH but the downlink data channel such as the PDSCH (PhysicalDownlink Shared Channel) of the LTE in the duration in which the radioterminal is activated cyclically is also thinkable. For example, thecase of receiving the PDSCH of a predetermined radio resource withoutusing the PDCCH particularly at the time of the first-time transmission,as is the case with the successive resource assignment of the LTE(Semi-persistent scheduling), is one example thereof.

Basically, the DRX is controlled based on a plurality of the timers asshown in FIG. 5, and each timer is defined as described below (theNon-patent literature 2).

-   -   drx-InactivityTimer: Specifies the number of consecutive        subframes (PDCCH-subframes) after successfully decoding a PDCCH        indicating an initial UL (Uplink) or DL (Downlink) user data        scheduling for the UE.    -   HARQ RTT Timer: This parameter specifies the minimum amount of        subframess before a DL HARQ retransmission is expected by the        UE.    -   drx-RetransmissionTimer: Specifies the maximum number of        consecutive subframes for as soon as a DL retransmission is        expected by the UE.

The length of each timer is specified in the Non-patent literature 2 andthe Non-patent literature 4. For example, approximately twenty types ofthe lengths can be set in a range from 1 ms to 2560 ms with thedrx-InactivityTimer, and several types can be set in a range from 1 msto 33 ms with the drx-RetransmissionTimer. For the system of FDD(Frequency Division Duplex) the HARQ RTT Timer is set to 8 ms.

The DRX control employing these timers will be explained by employingFIG. 5.

At first, the UE, upon reception of the new DL data during theOn-Duration, starts (restarts) the drx-InactivityTimer. Further,simultaneously therewith, the UE starts the HARQ RTT Timer. The UEstarts the drx-RetransmissionTimer simultaneously with expiry of theHARQ RTT Timer when the DL data cannot be successfully decoded,(basically, the DL data is retransmitted before thedrx-RetransmissionTimer expires). The UE stops thedrx-RetransmissionTimer when the DL data is received and can besuccessfully decoded. And, the UE moves to the period (Opportunity forDRX) in which the PDCCH does not need to be received simultaneously withexpiry of the drx-InactivityTimer.

Herein, in FIG. 5, the drx-RetransmissionTimer runs beyond the period ofthe On-Duration, and the UE successively receives the PDCCH beyond theOn-Duration. This period in which UE successively receives the PDCCH iscalled Active Time, and the On-Duration is equivalent to the minimumvalue of the Active Time. Thus, the reception period of a predeterminedchannel is equivalent to the Active Time. Further, while the UE stopsthe drx-RetransmissionTimer when the retransmitted DL data can besuccessfully decoded, the UE may continue to activate thedrx-RetransmissionTimer without stopping it. In this case, the UEextends the Active Time when either the drx-RetransmissionTimer or thedrx-InactivityTimer is running, and moves to the period in which thePDCCH does not need to be received at a time point when that both timersexpire. In such a manner, the UE determines whether to extend the ActiveTime in each DRX cycle, and behaves so as to be able to receive the DLdata without a delay.

Next, the DRX state (DRX level) control will be explained by employingFIG. 6.

As described previously, the DRX has two DRX states that are called theShortDRX and the LongDRX. Basically, the UE firstly starts from theShortDRX and transits to the LongDRX after a certain period elapses. Itis drxShortCycleTimer that is employed for determining a transition fromthis ShortDRX to the LongDRX, and the drxShortCycleTimer is defined asfollows (the Non-patent literature 2).

-   -   drxShortCycleTimer: Specifies the number of consecutive        subframes the UE shall follow the ShortDRX cycle.

FIG. 6 shows a situation in which the UE receives the DL data during theShortDRX, and can successfully decode it at a certain time point. The UEstarts (restarts) the drxShortCycleTimer at a time point when the DLdata can be successfully decoded. When the UE receives the new datawhile the drxShortCycleTimer is running, it again restarts thedrxShortCycleTimer at a time point when the above data can besuccessfully decoded.

On the other hand, when the UE does not receive the new data until thedrxShortCycleTimer expires as shown in FIG. 6, it transits to theLongDRX from the ShortDRX. And, when the UE receives the new data aftertransiting to the LongDRX, it again transits to the ShortDRX from theLongDRX.

Additionally, in a case of mentioning the restart of the timer, therestart basically signifies the restart from an initial value; however,the present invention is applicable even though the restart of the timeris differently signified. For example, the case in which the timer stopstemporarily, and thereafter, starts to run again from the above value ofthe stopping, and the like are thinkable.

Next, the DRX control method at the time of the CA in the radiocommunication system of the first exemplary embodiment will beexplained.

At first, the radio communication system of the first exemplaryembodiment independently performs operations (for example, extension ofthe Active Time) other than the DRX state control, out of a series ofoperations of the discontinuous reception (DRX) of the radio terminal(UE), respectively, and commonly takes the DRX state control on all thecomponent carriers (CCs) or one part thereof. As shown in FIG. 1, whenthe UE1 can simultaneously use the CC1 to the CC3, the UE activates thedrx-InactivityTimer, the HARQ RTT Timer, and the drx-RetransmissionTimeron each CC, and decides the Active Time. This makes it possible torealize a reduction in the power consumption of the UE according to theactual data reception on each CC at each the DRX cycle. On the otherhand, the following three methods are thinkable as a method ofcontrolling the DRX state.

1. Each CC has the drxShortCycleTimer, the drxShortCycleTimer isindependently activated on each CC, and a transition to the LongDRX fromthe ShortDRX is carried out at a time point when the drxShortCycleTimersexpire on all the CCs.

2. The CCs shares one drxShortCycleTimer, the drxShortCycleTimer isrestarted when the CC receiving at least one piece of the data exists ateach DRX cycle, and a transition to the LongDRX from the ShortDRX iscarried out at a time point when the drxShortCycleTimer expires.

3. Each CC has the drxShortCycleTimer. In addition, the CCs have oneseparate timer (CA-drxShortCycleTimer) (common to the CCs). At first,the drxShortCycleTimer is independently activated on each CC. When thedrxShortCycleTimer is started or restarted on any CC, theCA-drxShortCycleTimer is also started or restarted. And a transition tothe LongDRX from the ShortDRX is carried out at a time point when theCA-drxShortCycleTimer expires.

These methods make it possible to realize the DRX state control based onnot the data reception frequency of each CC but the total data receptionfrequency of each UE. Additionally, individually deactivating(Deactivation) the CCs that become unnecessary during the DRX controlmakes it possible to avoid the excessive power consumption of theterminal. Further, a transition to the ShortTDRX from the LongDRX iscarried out in such a manner that a transition to the ShortDRX iscarried out on all the CCs when the new data is received on any CC inthe On-Duration of the longDRX. However, the transition is not limitedhereto, and for example, the method in which, when the data is receivedat the consecutive N-time DRX cycles on a certain CC, all other CCs aswell transit to the ShortDRX, the method in which, when the new data isreceived on the CCs of M or more, all other CCs as well transit to theShortDRX, and the like are thinkable. However, the first-place method ispreferred from a viewpoint of taking the DRX state control based on thetotal data reception frequency of the UE.

Additionally, while this radio communication system has a preferredconfiguration in accordance with a specification of the 3GPP LTE, theconfiguration is not limited hereto.

In such a manner, in accordance with this exemplary embodiment, the DRXstate (DRX level) suitable for the data reception frequency can bemaintained, and yet selection of the CC responding to a communicationchannel quality and a load such as a traffic can be realized while thepower consumption is reduced when the radio terminal takes the controlof the discontinuous reception (DRX) at the time oftransmitting/receiving the data by simultaneously employing a pluralityof the component carriers (Component Carrier: CC) each having adifferent frequency (Carrier Aggregation: CA).

First Example

FIG. 7 is a view illustrating a situation of the DRX by CC of the radioterminal (UE), which explains the first example corresponding to thefirst exemplary embodiment.

In the example, the drxShortCycleTimer is activated on each CC, and atransition to the LongDRX from the ShortDRX is carried out at a timepoint when the drxShortCycleTimers expire on all the CCs. Herein, it isassumed that the terminal is firstly in a state of the ShortDRX, and thelength of the drxShortCycleTimer is equivalent to three times that ofthe ShortDRX cycle.

The UE starts the drxShortCycleTimers on all the CCs at the first-placeDRX cycle (the DRX cycle is counted in the ShortDRX). The data is notreceived on the CC2, whereby the CC2 moves to the non-reception period(Opportunity for DRX) after the PDCCH is received only in theOn-Duration (after it is confirmed that no data is transmitted). On theother hand, on the CC1 and the CC3, the data is received, the Activetimes are extended from the On-Durations, respectively, and thedrxShortCycleTimer is restarted at a time point when the data decodingis successfully carried out.

The data is received on all the CCs at the second-place DRX cycle, andthe drxShortCycleTimer is restarted after the data reception issuccessfully carried out, respectively.

Next, upon paying attention to the fifth-place DRX cycle, it can be seenthat the drxShortCycleTimer expires on the CC3. Conventionally, the CC3transits to the LongDRX at this time point; however the ShortDRX ismaintained without a transition to the LongDRX in the present invention.

Likewise, while the drxShortCycleTimer of the CC1 expires at thesixth-place DRX cycle, the ShortDRX is maintained uninterruptedly.

Upon paying attention to the seventh-place DRX cycle, the data isreceived on the CC1. Conventionally, the data cannot be received on theCC1 because the seventh-place DRX cycle is the timing of a transition tothe LongDRX; however the data reception is possible in the first examplebecause the ShortDRX is maintained uninterruptedly. In addition, thedrxShortCycleTimer is started again at this time.

The situation is similar with the CC3 in the eighth-place DRX cycle.

Thereafter, after the ShortDRX is successively carried out on each CC,the drxShortCycleTimer expires on the CC2 at the tenth-place DRX cycle,and the drxShortCycleTimers expire on the CC1 and CC3 at theeleventh-place DRX cycle. For this reason, all the CCs transit to theLongDRX after the twelfth-place DRX cycle. Additionally, when the datais not received particularly after the drxShortCycleTimer temporarilyexpires on a certain CC and yet when the drxShortCycleTimers expire onall the other CCs, a transition to the LongDRX is possible at its timepoint.

FIG. 8 is a view illustrating an operational flow of the communicationcontroller 14 of the UE1 in this example, and FIG. 9 is a viewillustrating an operational flow of the communication controller 24 ofthe eNB1 in this example.

In FIG. 8, the UE1 firstly initiates from the ShortDRX as the DRX state(DRX level) (Step 100), and starts the drxShortCycleTimer on each CC(Start drxShortCycleTimer on each CC) (Step 101).

The UE1 determines whether the downlink data (DL data) exists for eachCC in the initial On-Duration (DL data on CCn?) (Step 102).Continuously, the UE1 determines whether the downlink data was able tobe successfully decoded when the downlink data is received,(Successfully decoded?) (Step 103), and restarts the drxShortCycleTimer(Re-start drxShortCycleTimer) after it can be successfully decoded (orafter the HARQ process is finished) (Step 104).

Likewise, the UE1 determines whether the downlink data exists in theOn-Duration period (Step 105 and Step 102), performs the similaroperation when it exists, and continues to activate the remainingdrxShortCycleTimers without stopping them when it does not exist (Step103 and Step 104). And, the UE1 determines whether thedrxShortCycleTimer has expired for each CC (drxShortCycleTimer expired?)(Step 106).

When the drxShortCycleTimer has expired on a certain CC, the UE1confirms whether the drxShortCycleTimers expired (have expired) on allthe other CCs as well (drxShortCycleTimer expired on all CCs?) (Step107), and repeats the similar operation when the drxShortCycleTimershave not expired yet on the other CCs. That is, when the downlink datais received, the UE1 restarts the drxShortCycleTimer after the downlinkdata can be successfully decoded (Restart). Additionally, the case of,when the drxShortCycleTimer has temporarily expired on a certain CC andyet the drxShortCycleTimers have not expired on the other CCs, receivingthe downlink data again on the above CC should be referred to as not thestart but the restart because the above timer is not running; however anacquisition result is identical. To the contrary, when thedrxShortCycleTimers expire on all the CCs, the UE1 transits to theLongDRX (Start LongDRX) (Step 108).

Next, in FIG. 9, the communication controller 24 of the eNB1 starts thecontrol of the ShortDRX for UEx (x=1, 2, . . . , ) (Start UEx's ShortDRXcontrol) (Step 200).

At first, the communication controller 24 sends a DRX configurationmessage to the UEx (x=1, 2, . . . , ) (Send DRX configurationmessage)(Step 201), and starts the drxShortCycleTimer (StartdrxShortCycleTimer on each CC) (Step 202).

Next, the communication controller 24 determines whether the UEx is inthe On-Duration period (On-Duration?) (Step 203), and furthermoredetermines whether the data to be sent to the above UEx exists when itis in the On-Duration period (Data for UEx?) (Step 204). Thecommunication controller 24 decides which CC is used for transmittingthe data when sending the data, and proceeds to the subsequentoperations for each CC.

The communication controller 24 firstly confirms whether to send thedata for each CC (Send data on CCn?) (Step 207), and determines whetherthe data has been successfully decoded in the UE side, namely whether anacknowledge response (ACK) has been returned (or whether the HARQ hasbeen finished) when transmitting the data (Step 208). When transmittingthe data, the communication controller 24 confirms the reception of theacknowledge response, and thereafter, restarts the drxShortCycleTimer(Re-start drxShortCycleTimer) (Step 209). And, the communicationcontroller 24 determines whether the drxShortCycleTimer has expired(drxShortCycleTimer expired?) (Step 210), and confirms whether thedrxShortCycleTimers have expired also on all the other CCs when thedrxShortCycleTimer expires (has expired) (drxShortCycleTimer expired onall CCs?) (Step 205). When the drxShortCycleTimers expire on all theCCs, the communication controller 24 judges that the above UEx transitsto the LongDRX, and starts the LongDRX control (Start UEx's LongDRXcontrol) (Step 206).

Herein, in the LTE, the initial On-Duration, namely, the timing forstarting an operation of the drxShortCycleTimer is synchronized betweenthe UE and the eNB with the predetermined method (equation ofintroducing a DRX start offset).

Additionally, while the case in which the similar processing method wasperformed in the UE1 and eNB1 was explained in this example, the similarprocessing method does not need to be performed in the UE1 and eNB1 solong as the acquired result is identical. For example, the method ofthis example may be employed for the UE, and the method to be laterdescribed may be employed for eNB, or vice versa.

In such a manner, in the first example, a reduction in the powerconsumption of the UE can be realized at each DRX cycle while the DRXstate control suitable for the total data reception frequency of the UEis taken.

Further, employing this DRX control method makes the CC selection at thetime of the CA flexible, which enables the CC selection responding tothe communication channel quality and the load distribution between theCCs to be realized. For example, at the seventh-place and theeighth-place DRX cycles of FIG. 7, the drxShortCycleTimers expire on theCC1 and CC3, and conventionally, the CC1 and the CC3 cannot be usedbecause the seventh-place and the eighth-place DRX cycles become thenon-reception period (Opportunity for DRX) of the LongDRX, respectively.At this time, it might lead to deterioration in receptioncharacteristics that the communication channel quality of the CC2deteriorates, and yet is inferior as compared with that of the CC1 andCC3. Further, when a use rate of the CC2 is higher that of the CC1 andthe CC3, namely a load to the CC2 is higher, the influence such as adecline in a throughput might be produced upon not only the above radioterminal but also the other radio terminals. However the presentinvention is capable of avoiding these situations.

Modified Example of the First Example

FIG. 10 is a view for explaining a modified example of the first exampleof the present invention. In this example, similarity to the firstexample, the drxShortCycleTimer is activated on each CC, and atransition to the LongDRX from the ShortDRX is carried out at a timepoint when the drxShortCycleTimers expire on all the CCs.

A difference with the first example lies in a point that thedrxShortCycleTimer is not started on the CC in which thedrxShortCycleTimer has expired once even though the data is receivedafter the expiry, until the above CC temporarily transits to theLongDRX, and comes into the ShortDRX again.

Upon paying attention to the sixth-place DRX cycle, thedrxShortCycleTimer expires on the CC1, and conventionally, the CC1transits to the LongDRX; however the ShortDRX is continued also on theCC1 in the present invention because the drxShortCycleTimers of theother CCs have not expired.

Next, upon paying attention to the seventh-place DRX cycle, the data isagain received on the CC1; however the drxShortCycleTimer is not startedagain because the drxShortCycleTimer has expired once. This situation issimilar with the CC3 at the eighth-place DRX cycle. And, a transition tothe LongDRX is carried out at a time point when the drxShortCycleTimerof the CC2 having run to the end expires. Additionally, a configurationmay be made in such a manner that the drxShortCycleTimer is startedagain when a certain condition is met also after the drxShortCycleTimerhas expired once. For example, the case in which the data is receivedconsecutively N times, the case in which the data is again receivedafter T subframes without a transition to the LongDRX, and the like arethinkable.

It can be safely said that the method of the modified example of thefirst example is the aggressive DRX control method that aims at reducingthe consumption power of the UE all the more as compared with the firstexample.

Second Example

FIG. 11 is a view illustrating a situation of the DRX by CC of the radioterminal (UE), which explains the second example of the first exemplaryembodiment.

In this example, the UE activates the drx-InactivityTimer, thedrx-RetransmissionTimer, and the HARQ RTT Timer on each CC, and decidesthe Active Time; however, it commonly activates the drxShortCycleTimeramong the CCs, and transits to the LongDRX from the ShortDRX at a timepoint when this drxShortCycleTimer expires. Herein, it is assumed thatthe UE is firstly in a state of the ShortDRX, and the length of thedrxShortCycleTimer is equivalent to three times that of the ShortDRXcycle.

The UE firstly starts the drxShortCycleTimer at the first-place DRXcycle (the DRX cycle here is counted in the ShortDRX). In FIG. 11, theCC1 and the CC3 receive the data at the first-place DRX cycle, and theCC3 receives the data for a longer time than the CC1. Thereupon, the UErestarts the drxShortCycleTimer after the CC3 completes the datareception.

Next, the data is received on all the CCs at the second-place DRX cycle,and CC2 receives the data for a longest time, whereby the UE againrestarts the drxShortCycleTimer after the CC2 completes the datareception. Likewise, the UE restarts the drxShortCycleTimer so as tomatch with the CC having received most newly, and waits for expiry ofthe Timer. In FIG. 11, after the last data is received at theeighth-place DRX cycle, the drxShortCycleTimer expires at theeleventh-place DRX cycle, and the UE transits to the LongDRX.

FIG. 12 is a view illustrating an operational flow of the communicationcontroller 14 of the UE1 in this example, and FIG. 13 is a viewillustrating an operational flow of the communication controller 24 ofthe eNB1 in this example.

In FIG. 12, the communication controller 14 of the UE1 firstly initiatesfrom the ShortDRX as the DRX state (DRX level) (Step 300), and startsthe drxShortCycleTimer (Start drxShortCycleTimer) (Step 301).

The communication controller 14 determines whether the downlink dataexists on any CC in the initial On-Duration (DL data on any CC?) (Step302), and determines whether the downlink data was able to besuccessfully decoded (or the HARQ process has been finished) when thedownlink data is received (Successfully decoded?) (Step 303).

The communication controller 14 restarts the drxShortCycleTimer afterthe downlink data can be successfully decoded (or after the HARQ processis finished) (Re-start drxShortCycleTimer) (Step 304). Likewise, thecommunication controller 14 determines whether the downlink data existsin the On-Duration period, performs the similar operation when itexists, and continue to activate the remaining drxShortCycleTimerswithout stopping them when it does not exist. And, the communicationcontroller 14 determines whether the drxShortCycleTimer has expired(drxShortCycleTimer expired?) (Step 306), and transits to the LongDRXwhen it expires (has expired) (Start LongDRX) (Step 307).

Next, in FIG. 13, the communication controller 24 of the eNB1 starts thecontrol of the ShortDRX for the UEx (x=1, 2, . . . , ) (Start UEx'sShortDRX control) (Step 400).

At first, the communication controller 24 sends the DRX configurationmessage to the UEx (Send DRX configuration message) (Step 401), andstarts the drxShortCycleTimer (Step 402).

The communication controller 24 determines whether the UEx is in theOn-Duration period (On-Duration?) (Step 403), and furthermore determineswhether the data to be sent to the above UEx exists when the UEx is inthe On-Duration period (Data for UEx?) (Step 404). The communicationcontroller 24 determines whether the data has been successfully decodedin the UE side, namely whether an acknowledge response (ACK) has beenreturned (or whether the HARQ process has been finished) when the datais transmitted (ACK?) (Step 405).

The communication controller 24 restarts the drxShortCycleTimer afterconfirming the reception of the acknowledge response (Re-startdrxShortCycleTimer) (Step 406). And, the communication controller 24determines whether the drxShortCycleTimer has expired(drxShortCycleTimer expired?) (Step 407), and judges that the above UExtransits to the LongDRX when the drxShortCycleTimer expires (hasexpired), and starts the LongDRX control (Start UEx's LongDRX control)(Step 408).

An effect by this example, similarly to the first example, is that areduction in the power consumption of the UE can be realized in each DRXcycle while the DRX state control suitable for the data receptionfrequency of the UE is taken. Further, employing this DRX control methodmakes the CC selection in the case of CA flexible, which enables the CCselection according to the communication channel quality and the loaddistribution between the CCs to be realized. While the data receptionsituation (Active Time) needs to be shared among the CCs at each DRXcycle, this example has an advantage of making the number of the timersto be handled small as compared with the first example.

Third Example

FIG. 14 is a view illustrating a situation of the DRX by CC of the radioterminal (UE), which explains the third example of the first exemplaryembodiment.

In this example, the UE activates the drx-InactivityTimer, thedrx-RetransmissionTimer, and the HARQ RTT Timer on each CC, decides theActive Time, and activates the drxShortCycleTimer. In addition, the UEemploys CA-drxShortCycleTimer linked to this drxShortCycleTimer, andtransits to the LongDRX from the ShortDRX at a time point when theCA-drxShortCycleTimer expires. Herein, it is assumed that the UE isfirstly in a state of the ShortDRX, and the length of thedrxShortCycleTimer and the length of CA-drxShortCycleTimer is equivalentto three times that of the ShortDRX cycle, respectively.

The UE firstly starts the drxShortCycleTimers at the first-place DRXcycle (the DRX cycle is counted in the ShortDRX) on all the CCs, andstarts the CA-drxShortCycleTimer as well simultaneously therewith. InFIG. 14, the CC1 and the CC3 receives the data at the first-place DRXcycle, and the CC3 receives the data for a longer time than the CC1.Thereupon, the UE restarts the CA-drxShortCycleTimer after the CC3completes the data reception.

Next, all the CCs receive the data at the second-place DRX cycle, andthe CC2 receives the data for the longest time, whereby the UE restartsthe CA-drxShortCycleTimer again after the CC2 completes the datareception. Likewise, the UE restarts the drxShortCycleTimer so as tomatch with the CC having received the data most newly, and waits forexpiry of the Timer. Additionally, while the drxShortCycleTimer of theCC3 has expired at the fifth-place DRX cycle and the drxShortCycleTimerof the CC1 has expired at the sixth-place DRX cycle, theCA-drxShortCycleTimer has not expired yet, namely, there exists the CC(CC2) in which the drxShortCycleTimer has not expired, whereby theShortDRX is successively maintained on the CC1 and CC3 as it stands. Inaddition, when the data is received newly on CC1 and CC3, the UE startsthe drxShortCycleTimer again. In FIG. 14, the drxShortCycleTimers expireon all the CCs at the eleventh-place DRX cycle, and thus, theCA-drxShortCycleTimer also expires, and the UE transits to the LongDRX.

An effect by this example as well, similarly to the first example, isthat a reduction in the power consumption of the UE can be realized ateach DRX cycle while the DRX state control suitable for the datareception frequency of the UE is taken. Further, employing this DRXcontrol method makes the CC selection at the time of the CA flexible,which enables the CC selection according to the communication channelquality and the load distribution between the CCs to be realized. Ascompared with the first example, this example needs to have one timernewly; however this example has an advantage that it is enough fordetermining the DRX state control based one timer (theCA-drxShortCycleTimer). Additionally, while it was assumed that thelength of the drxShortCycleTimer and that of the CA-drxShortCycleTimerwere identical to each other, they may differ from each other.

FIG. 15 is a view illustrating an operational flow of the communicationcontroller 14 of the UE1 in this example, and FIG. 16 is a viewillustrating an operational flow of the communication controller 24 ofthe eNB1 in this example.

In FIG. 15, the UE firstly initiates from the ShortDRX as the DRX state(DRX level) (Step 500), starts the drxShortCycleTimer on each CC, and inaddition, starts one CA-drxShortCycleTimer (Start drxShortCycleTimer oneach CC and CA-drxShortCycleTimer) (Step 501).

The UE determines whether the downlink data (DL data) exists for each CCin the initial On-Duration (DL data on CCn?) (Step 502), determineswhether the downlink data was able to be successfully decoded(Successfully decoded?) when the downlink data is received (Step 503),and restarts the drxShortCycleTimer of each CC and theCA-drxShortCycleTimer after the downlink data can be successfullydecoded (or the HARQ process is finished) (Re-start drxShortCycleTimerand CA-drxShortCycleTimer) (Step 504).

Likewise, the UE determines whether the downlink data exists in theOn-Duration period (Step 505), performs the similar operation when itexists, and continues to activate the remaining drxShortCycleTimerswithout stopping them when it does not exist. And, the UE determineswhether the drxShortCycleTimer has expired for each CC(drxShortCycleTimer expired?) (Step 506). When the drxShortCycleTimerhas expired on a certain CC, the UE confirms whether theCA-drxShortCycleTimer expired (has expired) (CA-drxShortCycleTimerexpired?) (Step 507), and repeats the similar operation when it has notexpired. On the contrary, the UE transits to the LongDRX when theCA-drxShortCycleTimer has expired (Start LongDRX) (Step 508).

Next, in FIG. 16, the communication controller 24 of the eNB1 starts thecontrol of the ShortDRX for the UEx (x=1, 2, . . . , ) (Start UEx'sShortDRX control) (Step 600).

At first, the eNB1 sends the DRX configuration message to the UEx (SendDRX configuration message) (Step 601), and starts theCA-drxShortCycleTimer (Start CA-drxShortCycleTimer (Step 602).

The eNB1 determines whether the UEx is in the On-Duration period(On-Duration?) (Step 603), and furthermore determines whether the datato be sent to the above UEx exists when the UEx is in the On-Durationperiod (Data for UEx?) (Step 604). When the eNB1 transmits the data, itdetermines whether the data has been successfully decoded in the UEside, namely whether an acknowledge response (ACK) has been returned (orwhether the HARQ process has been finished) (ACK?) (Step 605).

The eNB1 restarts the CA-drxShortCycleTimer after confirming thereception of the acknowledge response (Re-start CA-drxShortCycleTimer)(Step 606).

And, the eNB1 returns to the Step 603, determines whether the UEx is inthe On-Duration period (On-Duration?) (Step 603), and furthermoredetermines whether the data to be sent to the above UEx exists when theUEx is in the On-Duration period (Data for UEx?). When the data is nottransmitted, the eNB1 determines whether the CA-drxShortCycleTimer hasexpired (CA-drxShortCycleTimer expired?) (Step 607), judges that theabove UEx transits to the LongDRX when the CA-drxShortCycleTimer expires(has expired), and starts the control of the LongDRX (Start UEx'sLongDRX control) (Step 608).

Modified Example of the Third Example

FIG. 17 is a view for explaining a modified example of the third exampleof the first exemplary embodiment.

In this example, similarly to the third example, the UE activates thedrx-InactivityTimer, the drx-RetransmissionTimer, and the HARQ RTT Timeron each CC, decides the Active Time, and activates thedrxShortCycleTimer. In addition, the UE employs theCA-drxShortCycleTimer linked to this drxShortCycleTimer, and transits tothe LongDRX from the ShortDRX at a time point when theCA-drxShortCycleTimer expires. A difference with the third example liesin a point of basically linking the CA-drxShortCycleTimer to thedrxShortCycleTimer on one CC, out of a plurality of the CCs, andactivating it.

The UE firstly starts the drxShortCycleTimers at the first-place DRXcycle (the DRX cycle is counted in the ShortDRX) on all the CCs, andstarts the CA-drxShortCycleTimer as well simultaneously therewith. InFIG. 17, the CC1 and the CC3 receive the data at the first-place DRXcycle, and the UE links the CA-drxShortCycleTimer to thedrxShortCycleTimer of the CC1, and activates the CA-drxShortCycleTimerherein as an example. The data is also received on the CC1 at thesecond-place DRX cycle, and the drxShortCycleTimer is restarted. Forthis, the CA-drxShortCycleTimer is also restarted likewise.

Next, the drxShortCycleTimer of the CC1 expires at the sixth-place DRXcycle. Thereupon, the UE confirms whether the drxShortCycleTimers arerunning on the other CCs (the CC2 and the CC3). In FIG. 17, the UEsynchronizes the CA-drxShortCycleTimer with the drxShortCycleTimer ofthe CC2 because the drxShortCycleTimer of CC2 is still running.

On the other hand, while the drxShortCycleTimer of the CC2 and theCA-drxShortCycleTimer expire at the tenth-place DRX cycle, thedrxShortCycleTimer of the CC3 is still running, whereby the UEre-synchronizes the CA-drxShortCycleTimer with the drxShortCycleTimer ofthe CC3. And, the UE transits to the LongDRX because thedrxShortCycleTimer of the CC3 and the CA-drxShortCycleTimer expire atthe eleventh-place DRX cycle, and no CC in which the drxShortCycleTimeris running exits.

This modified example, as compared with the third example, has anadvantage that it is easy to update the CA-drxShortCycleTimer.

The Radio Communication System of the Second Exemplary Embodiment

FIG. 18 is a view illustrating an example of a schematic configurationof the radio communication system of the second exemplary embodiment.

This radio communication system of the second exemplary embodimentincludes a radio base station eNB2 and a radio terminal UE2. Herein, theUE2 has completed a connection establishment (RRC Connection) forcommunicating with the eNB2. Further, the UE2 is assigned CC1 to CC4 asthe Component Carrier (CC) capable of carrying out the CarrierAggregation (CA), and is in a state of being able to simultaneouslyreceive the data on the CCs 1 to 4. Additionally, each frequency of CC1to CC4 may be continuous or discontinuous, and in addition, eachfrequency band of CC1 to CC4 may be identical or different. In addition,the eNB2 notifies a parameter of the DRX to the UE2, and the UE2 carriesout the necessary setting (for example, the setting of expiry values ofthe DRX-related timers, and the like) according to the above parameter.Herein, an example of this exemplary embodiment in the second radiocommunication system shows the case in which the CC1 and the CC2(subset1), and the CC3 and the CC4 (subset2) operate as a pair,respectively. As a factor that this Subset is configured (even thoughthere is no ground that the Subset has to be configured without fail),the case in which services basically differ among the Subsets (FTP,VoIP, Streaming, etc.), the case in which frequency bands differs amongthe Subsets, the case in which a cell coverage differs among theSubsets, the types of the CC differ (for example, the type that can beused commonly to all Release versions, the type that can be used after aspecific Release version, the type that can be used only under aspecific condition, and the like) and the like are thinkable. At thistime, the parameter of the DRX may be common to the CC1 to the CC 4, andthe parameter may be common within the identical Subset, and may bedifferent Subset by Subset.

Next, the DRX control at the time of the CA in the radio communicationsystem of the second exemplary embodiment will be explained.

As shown in FIG. 18, when the UE2 can simultaneously use the CC1 to theCC4, the UE2 activates the drx-InactivityTimer, the HARQ RTT Timer, andthe drx-RetransmissionTimer on each CC, and decides the Active Time.This makes it possible to realize a reduction in the power consumptionof the UE responding to the actual data reception on each CC at each DRXcycle. Additionally, as a method of controlling the DRX state, themethod is employed of controlling the DRX state in such a manner thatthe DRX state may differ Subset by Subset with the DRX state within theSubset of the CC kept identical. As the detailed operation, thefollowing three operations are thinkable.

1. Each CC has the drxShortCycleTimer, the drxShortCycleTimer isindependently activated on each CC, and at a time point when thedrxShortCycleTimers expire on all the CCs within the Subset, all the CCswithin the above Subset transit to the LongDRX from the ShortDRX.

2. The CCs within the Subset share one drxShortCycleTimer, thedrxShortCycleTimer is restarted when there is at least one CC havingreceived the data at each DRX cycle, and all the CCs within the aboveSubset transit to the LongDRX from the ShortDRX at a time point when thedrxShortCycleTimer expires.

3. Each CC has the drxShortCycleTimers. In addition, each Subset has oneseparate timer (CA-drxShortCycleTimer) (common to the CCs). At first,the drxShortCycleTimer is independently started on each CC. When thedrxShortCycleTimer is started or restarted on any CC, theCA-drxShortCycleTimer is also started or restarted. And, all the CCswithin the above Subset transit to the LongDRX from the ShortDRX at atime point when the CA-drxShortCycleTimer expires.

These methods make it possible to realize the DRX state control based onnot the data reception frequency of each CC but the total data receptionfrequency within the Subset of each UE. These methods, as mentionedabove, are effective in the case in which the service differs among theSubset, the case in which the frequency band differs, and the like.

Additionally, while this radio communication system has a preferredconfiguration in accordance with a specification of the 3GPP LTE, theconfiguration is not limited hereto.

Fourth Example

FIG. 19 is a view illustrating a situation of the DRX by CC of the radioterminal (UE), which explains the fourth example of the second exemplaryembodiment.

Further, in the example, the UE activates the drxShortCycleTimer on eachCC, it transits to the LongDRX from the ShortDRX at a time point whenthe drxShortCycleTimers expire on all the CCs within the Subset. Herein,it is assumed that the terminal is firstly in a state of the ShortDRX,and the length of the drxShortCycleTimer is equivalent to three timesthat of the ShortDRX cycle. Additionally, it is assumed that the DRXparameter is common to all the CCs.

At first, attention is paid to the CC1 and CC2 (the Subset1). The UEstarts the drxShortCycleTimers on both CCs at the first-place DRX cycle(the DRX cycle is counted in the ShortDRX). The CC2 moves to thenon-reception period (Opportunity for DRX) after receiving the PDCCHonly in the On-Duration because the data is not received on the CC2.

On the other hand, on the CC1, the data is received, the Active time isextended from the On-Duration, and the drxShortCycleTimer is restartedat a time point when the data decoding is successfully carried out.

Next, upon paying attention to the sixth-place DRX cycle, it can be seenthat the drxShortCycleTimer expires on the CC1. Conventionally, the CC1transits to the LongDRX at this time point; however, the ShortDRX ismaintained in this example.

Further, the data is received on the CC1 at the seventh-place DRX cycle.Conventionally, the data cannot be received on the CC1 because thisperiod is a period of transition to the LongDRX; however the datareception is possible in this example because the ShortDRX is maintainedas it stands. Additionally, at this time, the drxShortCycleTimer isstarted again on the CC1. Thereafter, after the ShortDRX is successivelycarried out on each CC, the drxShortCycleTimer of the CC2 expires at thetenth-place DRX cycle and the drxShortCycleTimer of the CC1 expires atthe eleventh-place DRX cycle, respectively. For this reason, all the CCswithin the Subset1 transit to the LongDRX since the twelfth-place DRXcycle. Additionally, when the data is not received particularly afterthe drxShortCycleTimer temporarily has expired on a certain CC, and yetwhen the drxShortCycleTimers have expired on all the other CCs, atransition to the LongDRX is possible at its time point.

Next, attention is paid to the CC3 and CC4 (the Subset2). The basicoperation is identical to that of the Subset1. The drxShortCycleTimersare firstly started on both of the CC3 and CC4 at the first-place DRXcycle. Herein, the drxShortCycleTimers are started after the datareception is completed because the data is received on both. And, afterthe drxShortCycleTimer of the CC4 expires at the fourth-place DRX cycle,the drxShortCycleTimer of the CC3 expires at the fifth-place DRX cycle.Thus, at this time point, the CCs of the Subset2 transit to the LongDRXfrom the ShortDRX.

On the other hand, both of the CC3 and the CC4 transit to the ShortDRXfrom the LongDRX because the data is received on the CC3 at the nextLongDRX cycle. And, the drxShortCycleTimers are started, respectively.

This brings about the case in which the DRX state of the Subset1 (CC1and CC2) differs from that of the Subset2 (CC3 and CC4). For example,while the DRX state of the Subset1 is the ShortDRX at the sixth-place tothe eighth-place DRX cycles, the DRX state of the Subset2 is theLongDRX.

In such a manner, taking the DRX state control for each Subset in thisexample makes it possible to realize a reduction in the powerconsumption of the UE at each DRX cycle while taking the DRX statecontrol suitable for the data reception frequency by each Subset.Further, employing this DRX control method makes the CC selection at thetime of the CA flexible, which enables the CC selection according to thecommunication channel quality and the load distribution between the CCsto be realized.

The Radio Communication System of the Third Embodiment

FIG. 20 is a view illustrating an example of a schematic configurationof the radio communication system of another exemplary embodiment of thepresent invention.

This third radio communication system includes a radio base station eNB3and a radio terminal UE3. Herein, the UE3 has completed a connectionestablishment (RRC Connection) for communicating with the eNB3. Further,the UE3 is assigned CC1 to CC3 as the Component Carrier (CC) capable ofcarrying out the Carrier Aggregation (CA), and is already in a state ofbeing able to simultaneously receiving the data on the CC1 to the CC3.However, the CC2 is a DL CC of Serving cell. Herein, as the definitionof the Serving cell, the CC that is used also when the CA is not carriedout, the CC where a radio terminal camped before the radio terminalbecomes active (RRC_Connected) (or the CC that can be camped), the CCwhere the radio terminal receives system information (SystemInformation), and the like are thinkable. Further, the CC of the Servingcell is called a serving carrier (Serving carrier) or an anchor carrier(Anchor carrier). Additionally, each frequency of CC1 to CC3 may becontinuous or discontinuous, and in addition, each frequency band of CC1to CC3 may be identical or different. In addition, the eNB3 notifies theparameter of the DRX to the UE3, and the UE3 carries out the necessaryconfiguration (for example, the setting of expiry values of theDRX-related timers, and the like) according to the above parameter. Atthis time, while it is expected that the parameter of the DRX may becommon to the CC1 to the CC3, the parameter may differ CC by CC.

Next, the DRX control method at the time of the CA in the radiocommunication system of the third exemplary embodiment will beexplained.

At first, the third radio communication system of the present inventionindependently performs operations (for example, extension of the ActiveTime) other than the DRX state (DRX level) control, out of a series ofoperations of the discontinuous reception (DRX) of the radio terminal(UE), on all component carriers (CCs) or one part thereof, respectively,and commonly takes the DRX state control. As shown in FIG. 20, when theUE3 can simultaneously use the CC1 to the CC3, the UE3 activates thedrx-InactivityTimer, the HARQ RTT Timer, and the drx-RetransmissionTimeron each CC, and decides the Active Time. This makes it possible torealize a reduction in the power consumption of the UE according to theactual data reception on each CC at each the DRX cycle.

On the other hand, as the method of controlling the DRX state (DRXlevel), only a specific CC has the drxShortCycleTimer, and thedrxShortCycleTimer is activated on the above CC, and all the CCs transitto the LongDRX from the ShortDRX at a time point when thedrxShortCycleTimer expires. Herein, as a specific CC, the CC of theServing cell in FIG. 20 is thinkable. The CC of the Serving cell isdefined in various ways, and for example, the CC where a radio terminalcamped at a time point when the radio terminal has become active(RRC_Connected), the CC where the radio terminal receives theconfiguration message (Configuration message) of the CA, the CC wherethe radio terminal received basic information of the cell such as thesystem information (System Information), and the like are thinkable.

These methods make it possible to realize the DRX state control based onnot the data reception frequency of each CC but the data receptionfrequency on the CC of the Serving cell of each UE, and above all, theDRX state control based on the total data reception frequency.Additionally, individually deactivating (Deactivation) the CCs havingbecome unnecessary during the DRX control makes it possible to avoid theexcessive power consumption of the terminal. Further, with regard to atransition to the ShortDRX from the LongDRX, a configuration is made insuch a manner that when the CC of the Serving cell receives the new datain the On-Duration of the LongDRX, all the CCs transits to the ShortDRX.However, the transition is not limited hereto, and for example, themethod in which the CC of the Serving cell receives the data at theconsecutive N-time DRX cycles, all other CCs also transit to theShortDRX, the method in which M CCs or more receive the new data besidesthe CC of the Serving cell, all other CCs also transit to the ShortDRX,and the like are thinkable. However, the first-place method is preferredfrom a viewpoint of taking the DRX state control based on the total datareception frequency of the UE.

In addition, when the CCs assigned to the radio terminal are dividedinto the Subsets, a configuration may be made in such a manner that onlya specific CC within the Subset has the drxShortCycleTimer, thedrxShortCycleTimer is activated on the above CC, and all the CCs withinthe Subset transit to the LongDRX from the ShortDRX at a time point whenthe drxShortCycleTimer expires.

Additionally, while this radio communication system includes a preferredconfiguration in accordance with the specification of the 3GPP LTE, theconfiguration is not limited hereto.

Fifth Example

FIG. 21 is a view illustrating a situation of the DRX by CC of the radioterminal (UE), which explains the fifth example of the third exemplaryembodiment.

In the example, while the UE activates the drx-InactivityTimer, thedrx-RetransmissionTimer, and the HARQ RTT Timer on each CC and decidesthe Active Time, it activates the drxShortCycleTimer only on the CC ofthe Serving cell, and transits to the LongDRX from the ShortDRX at atime point when this drxShortCycleTimer expires. Herein, it is assumedthat the UE is firstly in a state of the ShortDRX, and the length of thedrxShortCycleTimer is equivalent to three times that of the ShortDRXcycle.

The UE firstly starts the drxShortCycleTimer at the first-place DRXcycle (the DRX cycle is counted in the ShortDRX). In FIG. 21, the CC2and the CC3 receive the data at the first-place DRX cycle. The UErestarts the drxShortCycleTimer after the data reception on the CC2 iscompleted because the drxShortCycleTimer is controlled responding to thedata reception situation of the CC2. Next, all the CCs receive the dataat the second-place DRX cycle; however, the UE again restarts thedrxShortCycleTimer after the data reception on the CC2 is completed alsoso as to match with the data reception situation of the CC2 Likewise,the UE restarts the drxShortCycleTimer so as to match with the datareception situation of the CC2, and waits for the expiry of the abovetimer. In FIG. 21, after the last data is received at the seventh-placeDRX cycle, the drxShortCycleTimer expires at the tenth-place DRX cycle,and the UE transits to the LongDRX.

This DRX control method is most effective in a case of carrying out theCA, which basically uses the CC of the Serving cell at first, and inaddition, uses other CCS when the data that should be transmittedexists. This makes it possible to realize a reduction in the powerconsumption of the UE at each DRX cycle while taking the DRX statecontrol suitable for the total data reception frequency of the UE. Inaddition, employing this DRX control method makes the selection of theadditional CCs other than the CC of the Serving cell at the time of theCA flexible, which enables the CC selection according to thecommunication channel quality and the load distribution between the CCsto be realized.

FIG. 22 is a view illustrating an operational flow of the communicationcontroller 14 of the UE1 in this example, and FIG. 23 is a viewillustrating an operational flow of the communication controller 24 ofthe eNB1 in this example.

In FIG. 22, the UE1 firstly initiates from the ShortDRX as the DRX state(DRX level) (Step 700), and starts the drxShortCycleTimer (StartdrxShortCycleTimer) (Step 701).

The UE1 determines whether the downlink data (DL data) exists on CC2(Serving cell) in the initial On-Duration (DL data on CC2?) (Step 702),and determines whether the downlink data was able to be successfullydecoded (or whether the HARQ process has been finished (Successfullydecoded?) when the downlink data has received (Step 703).

The UE1 restarts the drxShortCycleTimer after the downlink data can besuccessfully decoded (or after the HARQ process is finished) (Re-startdrxShortCycleTimer (Step 704). Likewise, the UE1 determines whether thedownlink data exists on the CC2 in the On-Duration period (Step 705),performs the similar operation when it exists, and continue to activatethe remaining drxShortCycleTimers without stopping them when it does notexist. And, the UE1 determines whether the drxShortCycleTimer hasexpired (drxShortCycleTimer expired?) (Step 706), and transits to theLongDRX when the drxShortCycleTimer expires (or has expired) (StartLongDRX) (Step 707).

On the other hand, in FIG. 23, the communication controller 24 of theeNB1 starts the control of the ShortDRX for the UEx (x=1, 2, . . . , )(Start UEx's ShortDRX control) (Step 800).

At first, the communication controller 24 sends the DRX configurationmessage (DRX configuration message) to the UEx (Step 801), and startsthe drxShortCycleTimer (Step 802). The communication controller 24determines whether the UEx is in the On-Duration period (On-Duration?)(Step 803), and furthermore determines whether the data to be sent tothe above UEx exists when the UEx is in the On-Duration period (Data forUEx?) (Step 804). The communication controller 24 determines whether thedata has been successfully decoded in the UE side, namely whether anacknowledge response (ACK) has been returned (or whether the HARQprocess has been finished) when the data is transmitted, (ACK?) (Step805). The communication controller 24 restarts the drxShortCycleTimerafter confirming the reception of the acknowledge response (Re-startdrxShortCycleTimer) (Step 806). And, the communication controller 24determines whether the drxShortCycleTimer has expired(drxShortCycleTimer expired?) (Step 807), and judges that the above UExtransits to the LongDRX when the drxShortCycleTimer expires (hasexpired), and starts the control of the LongDRX (Start UEx's LongDRXcontrol (Step 808).

Above, while the exemplary embodiments described so far assumes that thedownlink control channel (PDCCH) and corresponding downlink data channel(PDSCH) corresponding are transmitted on each of the CCs that can beused in the case of CA, in the LTE the case in which the PDCCH istransmitted on a specific CC or on the CC different from the PDSCH isalso being investigated. In this case, the determination as to whetherthe data exists for each CC in the radio terminal side is made based onwhether the PDSCH of the above each CC has been scheduled either on theabove each CC or by the received PDCCH.

Further, the DRX control by the UE in the case of the CA, andparticularly, the operation of transiting to the LongDRX from theShortDRX in the DRX state (DRX level) control were explained. However,the point of the present invention is applicable to a transition to theIdle state from the DRX operation. That is, it is thinkable that withthe case in which the UE transits to the Idle state from the DRX(particularly, the LongDRX), the above transition is controlled by thetimer that the eNB and/or the UE maintains, and in this case, commonlycontrolling the timer among the CCs where the CA is performed enablesthe state transition to the Idle from the DRX to be realized accordingto the total activities of the UE. Further, with the case of the systemin which the Active Time is commonly configured, the point of thepresent invention can be also applied to the drx-InactivityTimer insteadof the drxShortCycleTimer.

In addition, it is also possible to apply the point of the presentinvention to measurement (Measurement) of the neighboring cells and thesuccessive resource assignment (Semi-persistent scheduling) by the UE inthe case of the CA besides the DRX control. In the Measurement, forexample, the method is thinkable in which also when the measurementparameter configuration (Measurement configuration) is shared, theactual measurement (Measurement) is performed independently on each CC,and the report (Measurement report) is shared. At this time, onrespective UL CC corresponding to the each DL CC the measurement reportmay be performed, and on a certain CC the measurements report may beperformed together. Further, in the implicit resource release (Implicitrelease) of Semi-persistent scheduling, there exists the method ofcommonly controlling the counts of not-yet-used resources of the uplink(Uplink: UL) etc. among the CCs. For example, the method of, when the ULresources previously assigned to all the CCs are not used yet, countingthe above resources, and releasing the UL resource when the above valueexceeds a predetermined value (ImplicitReleaseAfter: Non-Patentliteratures 2 and 4), the method of counting the not-yet-used resourceon each CC, and releasing the UL resource when the count values exceedpredetermined values on all the CCs, respectively, and the like arethinkable.

In addition, while “3GPP LTE” was expected as the radio communicationsystem in the exemplary embodiments described so far, a target of thepresent invention is not limited to hereto, and the present invention isapplicable to 3GPP WCDMA (Wideband Code Division Multiple Access), GSM(Global System for Mobile communications), WiMAX (Worldwideinteroperability for Microwave Access) and the like.

Hereinafter, yet specific examples are described.

When the DRX is set, the terminal (UE) performs the following operationsfor each subframe without fail.

When the ShortDRX Cycle is used and yet [(SFN*10)+subframe number]modulo (shortDRX-Cycle)=(drxStartOffset) modulo (shortDRX-Cycle), orwhen the LongDRX Cycle is used and yet [(SFN*10)+subframe number] modulo(longDRX-Cycle)=drxStartOffset), the UE starts onDurationTimer on eachActivated component carrier if the Carrier Aggregation is set, and theUE starts onDurationTimer otherwise. Wherein, SFN is System FrameNumber.

When the HARG RTT Timer expires at the present subframe and yet the dataof soft buffer of the above HARQ process is not successfully decoded,the UE starts the drx-RetransmissionTimer for the above HARQ process onthe above component carrier if the Carrier Aggregation is set, and theUE starts the drx-RetransmissionTimer for the above HARQ processotherwise.

When a DRX Command MAC control element is received, the UE stops theonDurationTimer on the above component carrier and yet stops thedrx-InactivityTimer on the above component carrier if the CarrierAggregation is set, and the UE stops the ondurationtimer and yet stopsthe drx-InactivityTimer otherwise.

When the drx-InactivityTimer is finished, or when the DRX Command MACcontrol element is received in the subframe, the UE starts or restartsthe drxShortCycleTimer on the above component carrier and yet uses theShort DRX cycle on the above component carrier if the CarrierAggregation is set and yet the Short DRX cycle is set, and the UE usesthe Long DRX cycle on the above component carrier otherwise.

When the drx-InactivityTimer is finished, or when the DRX Command MACcontrol element is received in the subframe, the UE starts or restartsthe drxShortCycleTimer and yet uses the Short DRX cycle if the Short DRXcycle is set, and the UE uses the Long DRX cycle otherwise.

When the Carrier Aggregation is set, the UE uses the Long DRX cycle ifthe drxShortCycleTimer expires on the present subframe and yet thedrxShortCycleTimer expires (or has expired) on all the Activatedcomponent carriers other than the above component carrier, and the UEuses the Long DRX cycle if Carrier Aggregation is not set and yet thedrxShortCycleTimer expires on the present subframe.

The UE monitors the PDCCH for the PDCCH-subframe that is not necessaryfor the uplink transmission of a half-duplex FDD system and yet is notone part of the set measurement gap during the Active Time.

When the PDCCH clearly states the downlink transmission, or when thedownlink transmission is previously assigned to the above subframe, theUE starts the HARQ RTT Timer in the above HARQ process on the abovecomponent carrier and yet stops the drx-RetransmissionTimer in the aboveHARQ process on the above component carrier if the Carrier Aggregationis set, and the UE starts the HARQ RTT Timer in the above HARQ processand yet stops the drx-RetransmissionTimer in the above HARQ processotherwise.

When the PDCCH clearly states the new transmission (DL or UL), the UEstarts or restarts the drx-InactivityTimer on the above componentcarrier if the Carrier Aggregation is set, and the UE starts or restartsthe drx-InactivityTimer otherwise.

The UE does not report CQI/PMI/RI in PUCCH and nor transmits SRS in thetime other than the Active Time.

Additionally, while in the above-described exemplary embodiments andexamples, each part was configured with hardware, it may be configuredwith an information processing unit such as CPU that operates under aprogram. In this case, the program causes the CPU etc. to execute theabove-described operations.

Further, the content of the above-mentioned exemplary embodiments can beexpressed as follows.

(Supplementary note 1) A radio communication system in which a radioterminal is configured to communicate using a plurality of carriercomponents each having a different frequency, comprising:

a reception start timing control means that commonly controls a cycle ofa reception start timing for a predetermined channel among at least onepart of the component carriers assigned to the radio terminal: and

a reception control means that controls a reception period for saidpredetermined channel on at least one part of the component carriersassigned to said radio terminal, said reception period being startedfrom said reception start timing.

(Supplementary note 2) A radio communication system according toSupplementary note 1, wherein said reception control means controls thereception period for said predetermined channel to be started from saidreception start timing, based on a timer that runs on each of at leastone part of the component carriers assigned to said radio terminal.

(Supplementary note 3) A radio communication system according toSupplementary note 1 or Supplementary note 2, wherein said receptionstart timing control means selects one cycle of the reception starttiming from among at least two cycles or more of said reception starttiming each having a different length.

(Supplementary note 4) A radio communication system according toSupplementary note 3, wherein said reception start timing control meansselects said cycle of the reception start timing based on data receptionsituations on at least one part of the component carriers assigned tosaid radio terminal.

(Supplementary note 5) A radio communication system according toSupplementary note 3 or Supplementary note 4, wherein said receptionstart timing control means transits to the cycle of the reception starttiming which is longer than the current cycle of the reception starttiming, when new data is not received for a predetermined period on atleast one part of the component carriers assigned to said radioterminal.

(Supplementary note 6) A radio communication system according toSupplementary note 5, wherein said reception start timing control means:

comprises at least one timer that, when data is received duringmeasurement and the above data is successfully decoded, restart andmeasure a predetermined period, said timers configured correspondinglyto at least one part of the component carriers assigned to said radioterminal; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when said timer reachesa predetermined period.

(Supplementary note 7) A radio communication system according toSupplementary note 5, wherein said reception start timing control means:

comprises a timer that, when data is received during measurement on anyof at least one part of the component carriers assigned to said radioterminal and the above data is successfully decoded, restart themeasurement; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timings, when the measurementperiod of said timer reaches a predetermined period.

(Supplementary note 8) A radio communication system according toSupplementary note 5, wherein said reception start timing control means:

comprises:

at least one first timer that, when data is received during measurement,and the above data is successfully decoded, restart and measure apredetermined period, said first timer configured correspondingly to atleast one part of the component carriers assigned to said radioterminal; and

a second timer that restarts the measurement when said first timerrestarts the measurement, and measures a predetermined period; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when the measurementperiod of said second timer reaches a predetermined period.

(Supplementary note 9) A radio communication system according toSupplementary note 5, wherein said reception start timing control means:

comprises:

first timers that, when data is received during measurement and theabove data is successfully decoded, restart and measure a predeterminedperiod, said timers configured correspondingly to at least one part ofthe component carriers assigned to said radio terminal; and

a second timer that corresponds to any of said first timers, andrestarts the measurement when said corresponding first timer restartsthe measurement; and

causes said second timer to correspond to any of said first timers onmeasurement other than said corresponding first timer when themeasurement period of said second timer reaches a predetermined period,and transits to the cycle of the reception start timing which is longerthan the current cycle of the reception start timing when themeasurement period of said second timer again reaches a predeterminedperiod and all said first timers are not performing said measurement.

(Supplementary note 10) A radio communication system according to one ofSupplementary note 1 to Supplementary note 4, wherein said receptionstart timing control means:

comprises:

timers that, when data is received during measurement and yet the abovedata is successfully decoded, restart and measure a predeterminedperiod, said timers configured correspondingly to at least one part ofthe component carriers assigned to said radio terminal; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when all the timers arenot performing said measurement.

(Supplementary note 11) A radio communication system according to one ofSupplementary note 3 to Supplementary note 10, wherein said receptionstart timing control means transits to the cycle of the reception starttiming which is shorter than the current cycle of the reception starttiming on at least one part of said assigned component carriers or on apredetermined specific kind of the component carrier when the new datais received on at least one component carrier belonging to at least onepart of the component carriers assigned to said radio terminal.

(Supplementary note 12) A radio communication system according to one ofSupplementary note 1 to Supplementary note 4, wherein said receptionstart timing control means:

comprises a timer that, when data is received during measurement and theabove data is successfully decoded, restarts and measures apredetermined period, said timer configured correspondingly to aspecific kind of the component carrier, which belongs to the componentcarriers assigned to said radio terminal; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when the measurementperiod of said timer reaches a predetermined period.

(Supplementary note 13) A radio communication system according toSupplementary note 12, wherein said reception start timing control meanstransits to the cycle of the reception start timing, which is shorterthan the current cycle of the reception start timing, on at least onepart of said assigned component carriers or on said specific kind of thecomponent carrier, when the new data is received on said specific kindof the component carrier.

(Supplementary note 14) A radio communication system according toSupplementary note 12 or Supplementary note 13, wherein said specifickind of the component carrier is at least one of a component carrier ofa serving cell and an anchor component carrier.

(Supplementary note 15) A radio communication system according to one ofSupplementary note 1 to Supplementary note 11, wherein said receptionstart timing control means and/or said reception control means take acontrol for each of at least one Subset or more, said Subset being a setof the component carriers assigned to the radio terminal.

(Supplementary note 16) A radio communication system according to one ofSupplementary note 1 to Supplementary note 15, wherein said receptionstart timing control means and/or said reception control means take acontrol related to discontinuous reception.

(Supplementary note 17) A radio communication system according to one ofSupplementary note 1 to Supplementary note 16, wherein said receptioncontrol means separately controls the reception period for saidpredetermined channel to be started from said reception start timing oneach of at least one part of the component carriers assigned to saidradio terminal.

(Supplementary note 18) A radio communication system according to one ofSupplementary note 1 to Supplementary note 17, wherein said receptioncontrol means commonly controls the reception period for saidpredetermined channel to be started from said reception start timing oneach of at least one part of the component carriers assigned to saidradio terminal.

(Supplementary note 19) A radio terminal capable of communicating usinga plurality of carrier components each having a different frequency,comprising:

a reception start timing control means that commonly controls a cycle ofa reception start timing for a predetermined channel among at least onepart of the component carriers assigned to the radio terminal; and

a reception control means that controls a reception period for saidpredetermined channel on at least one part of the component carriersassigned to said radio terminal, said reception period being startedfrom said reception start timing.

(Supplementary note 20) A radio terminal according to Supplementary note19, wherein said reception control means controls the reception periodfor said predetermined channel to be started from said reception starttiming, based on a timer that runs on each of component carrierbelonging to at least one part of the component carriers assigned tosaid radio terminal.

(Supplementary note 21) A radio terminal according to Supplementary note19 or Supplementary note 20, wherein said reception start timing controlmeans selects one cycle of the reception start timing from among atleast two cycles or more of said reception start timing each having adifferent length.

(Supplementary note 22) A radio terminal according to Supplementary note21, wherein said reception start timing control means selects said cycleof the reception start timing based on data reception situations on atleast one part of the component carriers assigned to said radioterminal.

(Supplementary note 23) A radio terminal according to Supplementary note21 or Supplementary note 22, wherein said reception start timing controlmeans transits to the cycle of the reception start timing which islonger than the current cycle of the reception start timing, when newdata is not received for a predetermined period on at least one part ofthe component carriers assigned to said radio terminal.

(Supplementary note 24) A radio terminal according to Supplementary note23, wherein said reception start timing control means:

comprises at least one timer that, when data is received duringmeasurement, and the above data is successfully decoded, restarts andmeasures a predetermined period, said timer configured correspondinglyto a specific kind of the component carrier, out of the componentcarriers assigned to said radio terminal; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when said timer reachesa predetermined period.

(Supplementary note 25) A radio terminal according to Supplementary note23, wherein said reception start timing control means:

comprises a timer that, when data is received during measurement on anycomponent carrier belonging to of at least one part of the componentcarriers assigned to said radio terminal and the above data issuccessfully decoded, restart the measurement; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timings, when the measurementperiod of said timer reaches a predetermined period.

(Supplementary note 26) A radio terminal according to Supplementary note23, wherein said reception start timing control means:

comprises:

at least one first timer that, when data is received during measurement,and the above data is successfully decoded, restart and measure apredetermined period, said first timer configured correspondingly to atleast one part of the component carriers assigned to said radioterminal; and

a second timer that restarts the measurement when said first timerrestarts the measurement, and measures a predetermined period; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when the measurementperiod of said second timer reaches a predetermined period.

(Supplementary note 27) A radio terminal according to Supplementary note23, wherein said reception start timing control means:

comprises:

first timers that, when data is received during measurement and theabove data is successfully decoded, restart and measure a predeterminedperiod, said timers configured correspondingly to at least one part ofthe component carriers assigned to said radio terminal; and

a second timer that corresponds to any of said first timers, andrestarts the measurement when said corresponding first timer restartsthe measurement; and

causes said second timer to correspond to any of said first timers onmeasurement other than said corresponding first timer when themeasurement period of said second timer reaches a predetermined period,and transits to the cycle of the reception start timing which is longerthan the current cycle of the reception start timing when themeasurement period of said second timer again reaches a predeterminedperiod and all said first timers are not performing said measurement.

(Supplementary note 28) A radio terminal according to one ofSupplementary note 19 to Supplementary note 22, wherein said receptionstart timing control means:

comprises:

timers that, when data is received during measurement and yet the abovedata is successfully decoded, restart and measure a predeterminedperiod, said timers configured correspondingly to at least one part ofthe component carriers assigned to said radio terminal; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when all the timers arenot performing said measurement.

(Supplementary note 29) A radio terminal according to one ofSupplementary note 19 to Supplementary note 28, wherein said receptionstart timing control means transits to the cycle of the reception starttiming which is shorter than the current cycle of the reception starttiming on at least one part of said assigned component carriers or on apredetermined specific kind of the component carrier when the new datais received on at least one component carrier belonging to at least onepart of the component carriers assigned to said radio terminal.

(Supplementary note 30) A radio terminal according to one ofSupplementary note 19 to Supplementary note 22, wherein said receptionstart timing control means:

comprises a timer that, when data is received during measurement and yetthe above data is successfully decoded, restarts and measures apredetermined period, said timer configured correspondingly to aspecific kind of the component carrier, out of the component carriersassigned to said radio terminal; and

transits to the cycle of the reception start timing which is longer thanthe current cycle of the reception start timing, when said timer reachesa predetermined period.

(Supplementary note 31) A radio terminal according to Supplementary note30, wherein said reception start timing control means transits to thecycle of the reception start timing, which is shorter than the currentcycle of the reception start timing, on at least one part of saidassigned component carriers or on said specific kind of the componentcarrier, when the new data is received on said specific kind of thecomponent carrier.

(Supplementary note 32) A radio terminal according to Supplementary note30 or Supplementary note 31, wherein said specific kind of the componentcarrier is at least one of a component carrier of a serving cell and ananchor component carrier.

(Supplementary note 33) A radio terminal according to one ofSupplementary note 19 to Supplementary note 32, wherein said receptionstart timing control means and/or said reception control means take acontrol for each of at least one Subset or more, said Subset being a setof the component carriers assigned to the radio terminal.

(Supplementary note 34) A radio communication system according to one ofSupplementary note 19 to Supplementary note 33, wherein said receptionstart timing control means and/or said reception control means take acontrol related discontinuous reception.

(Supplementary note 35) A radio terminal according to one ofSupplementary note 19 to Supplementary note 34, wherein said receptioncontrol means separately controls the reception period for saidpredetermined channel to be started from said reception start timing oneach of at least one part of the component carriers assigned to saidradio terminal.

(Supplementary note 36) A radio terminal according to one ofSupplementary note 19 to Supplementary note 35, wherein said receptioncontrol means commonly controls the reception period for saidpredetermined channel to be started from said reception start timing oneach of at least one part of the component carriers assigned to saidradio terminal.

(Supplementary note 37) A radio base station for transmitting/receivingdata to/from a radio terminal capable of communicating using a pluralityof component carriers each having a different frequency that comprises areception start timing control means for commonly controlling a cycle ofa reception start timing for a predetermined channel among at least onepart of the component carriers assigned to said radio terminal, and areception control means for controlling a reception period for saidpredetermined channel to be started from said reception start timing onat least one part of the component carriers assigned to said radioterminal, said radio base station comprising a means that takessynchronization with the cycle of the reception start timing for thepredetermined channel to be controlled by said radio terminal.

(Supplementary note 38) A radio base station according to Supplementarynote 37, wherein said reception control means controls the receptionperiod for said predetermined channel to be started from said receptionstart timing, based on a timer that runs on each of at least one part ofthe component carriers assigned to said radio terminal.

(Supplementary note 39) A radio communication method in which a radioterminal is configured to communicate using a plurality of componentcarriers each having a different frequency, comprising:

commonly controlling a cycle of a reception start timing for apredetermined channel among at least one part of the component carriersassigned to the radio terminal; and

controlling a reception period for said predetermined channel on atleast one part of the component carriers assigned to said radioterminal, said reception period being started from said reception starttiming.

(Supplementary note 40) A radio communication method according toSupplementary note 39, comprising controlling the reception period forsaid predetermined channel to be started from said reception starttiming, based on a timer that runs on each of at least one part of thecomponent carriers assigned to said radio terminal.

(Supplementary note 41) A radio communication method according toSupplementary note 39 or Supplementary note 40, comprising commonlycontrolling the reception period for said predetermined channel to bestarted from said reception start timing on each of at least one part ofthe component carriers assigned to said radio terminal.

(Supplementary note 42) A program of a radio terminal capable ofcommunicating using a plurality of component carriers each having adifferent frequency, said program causing the radio terminal to execute:

a reception start timing control process of commonly controlling a cycleof a reception start timing for a predetermined channel among at leastone part of the component carriers assigned to the radio terminal; and

a reception control process of controlling a reception period for saidpredetermined channel on at least one part of the component carriersassigned to said radio terminal, said reception period being startedfrom said reception start timing.

(Supplementary note 43) A program according to Supplementary note 42,wherein said reception control process controls the reception period forsaid predetermined channel to be started from said reception starttiming, based on a timer that runs on each component carrier belongingto at least one part of the component carriers assigned to said radioterminal.

(Supplementary note 44) A program according to Supplementary note 42 orSupplementary note 43, wherein said reception control process commonlycontrols the reception period of said predetermined channel to bestarted from said reception start timing on each component carrierbelonging to at least one part of the component carriers assigned tosaid radio terminal.

Above, although the present invention has been particularly describedwith reference to the preferred embodiments and the examples, it shouldbe readily apparent to those of ordinary skill in the art that thepresent invention is not always limited to the above-mentionedembodiment and examples, and changes and modifications in the form anddetails may be made without departing from the spirit and scope of theinvention.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2009-230114, filed on Oct. 2, 2009, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   -   11 receiver    -   12 transmitter    -   13 signal processor    -   14 communication controller    -   21 receiver    -   22 transmitter    -   23 signal processor    -   24 communication controller    -   25 terminal manager

The invention claimed is:
 1. A radio communication system in which aradio terminal is capable of communicating with a radio base station byusing a plurality of component carriers (CCs) each having a differentfrequency, comprising: a first processor, comprising hardware,configured to commonly control a cycle of a reception start timing for apredetermined channel in the radio terminal among all of the CCs, whichare assigned to the radio terminal; a second processor, comprisinghardware, configured to activate a hybrid automatic repeat-request(HARQ) round trip timer (RTT)Timer and a drx-RetransmissionTimer foreach of the CCs, and in case that any of the CCs receives apredetermined signal, to start or re-start a drx-InactivityTimer, andwhen the drx-InactivityTimer expires, to start or re-start adrxShortCycleTimer; and a third processor, comprising hardwareconfigured to commonly carry out a transition to LongDRX on all of theCCs when the drxShortCycleTimer expires.
 2. The radio communicationsystem according to claim 1, wherein the predetermined channel is adownlink control channel (PDCCH), the reception start timing for thepredetermined channel is a start timing of a reception period(On-Duration), and the cycle of the reception start timing for thepredetermined channel is a DRX cycle.
 3. A radio terminal capable ofcommunicating with a radio base station by using a plurality ofcomponent carriers (CCs) each having a different frequency, comprising:a first processor, comprising hardware, configured to commonly control acycle of a reception start timing for a predetermined channel among allof the CCs, which are assigned to the radio terminal; a secondprocessor, comprising hardware, configured to activate a hybridautomatic repeat-request (HARQ) round trip time (RTT) Timer and adrx-RetransmissionTimer for each of the CCs, and in case that any of theCCs, receives a predetermined signal, to start or re-start adrx-InactivityTimer, and when the drx-InactivityTimer expires, to startor re-start a drxShortCycleTimer; and a third processor, comprisinghardware, configured to commonly carry out a transition to LongDRX onall of the CCs when the drxShortCycleTimer expires.
 4. The radioterminal according to claim 3, wherein the predetermined channel is adownlink control channel (PDCCH), the reception start timing for thepredetermined channel is a start timing of a reception period(On-Duration), and the cycle of the reception start timing for thepredetermined channel is a DRX cycle.
 5. A radio base station capable ofcommunicating with a radio terminal by using a plurality of componentcarriers (CCs) each having a different frequency, comprising: a fourthprocessor, comprising hardware, configured to synchronize a cycle of areception start timing for a predetermined channel, which is controlledby the radio terminal, and to communicate with the radio terminal,wherein the radio base station carries out transmission and reception ofa signal to and from the radio terminal having: a first processor,comprising hardware, configured to commonly control a cycle of areception start timing for a predetermined channel among all of the CCsassigned from the radio base station; a second processor, comprisinghardware, configured to activate a hybrid automatic repeat-request(HARQ) round trip time (RTT) Timer and a drx-RetransmissionTimer foreach of the CCs, and in case that any of the CCs receives apredetermined signal, to start or re-start a drx-InactivityTimer, andwhen the drx-InactivityTimer expires, to start or re-start adrxShortCycleTimer; and a third processor, comprising hardware,configured to commonly carry out a transition to LongDRX on all of theCCs when the drxShortCycleTimer expires.
 6. The radio base stationaccording to claim 5, wherein the predetermined channel is a downlinkcontrol channel (PDCCH), the reception start timing for thepredetermined channel is a start timing of a reception period(On-Duration), and the cycle of the reception start timing for thepredetermined channel is a DRX cycle.
 7. A radio communication method ofa radio terminal capable of communicating with a radio base station byusing a plurality of component carriers (CCs) each having a differentfrequency, comprising: commonly controlling a cycle of a reception starttiming for a predetermined channel among all of CCs which are assignedto the radio terminal; activating a hybrid automatic repeat-request(HARQ) round trip time (RTT) Timer and a drx-RetransmissionTimer foreach of the CCs, and in case that any of the CCs receives apredetermined signal, starting or re-starting a drx-InactivityTimer, andwhen the drx-InactivityTimer expires, starting or re-starting adrxShortCycleTimer; and commonly carrying out a transition to LongDRX onall of the CCs when the drxShortCycleTimer expires.
 8. The radiocommunication method of a radio terminal according to claim 7, whereinthe predetermined channel is a downlink control channel (PDCCH), thereception start timing for the predetermined channel is a start timingof a reception period (On-Duration), and the cycle of the receptionstart timing for the predetermined channel is a DRX cycle.
 9. A radiocommunication method in a radio base station capable of communicatingwith a radio terminal by using a plurality of component carriers (CCs)each having a different frequency, comprising: carrying out transmissionand reception of a signal to and from the radio terminal for commonlycontrolling a cycle of a reception start timing for a predeterminedchannel in the radio terminal among all of the CCs, which are assignedfrom the radio base station; activating a hybrid automaticrepeat-request (HARQ) round trip time (RTT) Timer and adrx-RetransmissionTimer for each of the CCs, and in case that any of theCCs receives a predetermined signal, starting or re-starting adrx-InactivityTimer, and when the drx-InactivityTimer expires, startingor re-starting a drxShortCycleTimer, and commonly carrying out atransition to LongDRX on all of the CCs when the drxShortCycleTimerexpires; and synchronizing a cycle of a reception start timing for apredetermined channel, which is controlled by the radio terminal, andcommunicating with the radio terminal.
 10. The radio communicationmethod in a radio base station according to claim 9, wherein thepredetermined channel is a downlink control channel (PDCCH), thereception start timing for the predetermined channel is a start timingof a reception period (On-Duration), and the cycle of the receptionstart timing for the predetermined channel is a DRX cycle.